This invention concerns liquid fuel injection nozzles for supplying atomized droplets of fuel to a combustion chamber arrangement in a gas turbine engine combustion system. It also concerns such combustion systems and gas turbine engines provided with such combustion systems.
It is known to improve atomization and placement or positioning of liquid fuels within gas turbine engine combustion chambers by the use of electrodes located so as to impart electrostatic charge to the fuel droplets. For example, U.S. Pat. No. 4,439,980 discloses a gas turbine engine wherein fuel is injected through a spray injection nozzle towards an electrode in a combustion chamber so that after it has left the injection nozzle, the fuel becomes electrostatically charged, and the strength of the electric field is adjusted to provide a spray characteristic said to produce an optimum engine performance.
The inventor believes that further increased control of fuel placement, vaporization and combustion intensity is desirable. This would lead to greater combustion stability, particularly at low fuel injection rates, and lower emission of pollutants from engines.
An object of the present invention is therefore to provide a liquid fuel injection nozzle suitable for a gas turbine engine combustion system, by means of which one or more of fuel atomization, vaporization, placement and combustion intensity may be more accurately controlled to produce an improved combustion performance.
According to the invention there is provided a liquid fuel injection nozzle for supplying atomized droplets of fuel to a combustion chamber in a gas turbine engine, the nozzle comprising a passage with an exit for the droplets to leave the nozzle, and electrode means disposed around the passage, the electrode means having sharp edge means positioned to impart electrostatic charge to the droplets as they leave the nozzle.
Preferably at least the sharp edge comprises an erosion resistant material and may comprise the exit of the nozzle. Alternatively, the electrode means may be adjacent the exit of the nozzle.
If desired, the relatively sharp edge may project substantially along a general direction of flow of fuel along the passage, or alternatively the sharp edge may project substantially across said general direction of flow of fuel.
The electrode arrangement may form at least part of a wall of the nozzle passage.
A gas turbine engine combustion system may comprise at least one liquid fuel injection nozzle formed according to the invention, and further electrode means connected to charging means arranged to electrostatically charge the further electrode means at predetermined polarities with respect to the nozzle electrode means.
In an embodiment a gas turbine engine combustion system comprises:
a combustion main chamber,
a combustion pre-chamber upstream thereof and opening into the main chamber, the pre-chamber being of smaller flow area than the main chamber and being disposed about a longitudinal axis,
a burner face at an upstream end of the pre-chamber,
a preswirler assembly comprising a plurality of preswirl passages communicating with the upstream end of the pre-chamber for supplying a preswirled air/fuel mixture to the pre-chamber, the preswirl passages being disposed about the longitudinal axis,
a plurality of liquid fuel atomizing injection nozzles formed according to the invention and located in the preswirl passages to inject atomized liquid fuel thereinto,
charging means operable to selectively electrostatically charge the nozzle electrode means at a pre-determined polarity thereby to impart electrostatic charge to the atomized fuel,
preswirl electrode means forming at least portions of the preswirl passages, and
charging means operable to selectively electrostatically charge the preswirl electrode means at the same polarity as the nozzle electrode means, thereby to repel the atomized injected fuel from the preswirl passage portions.
There may be provided a first burner electrode means associated with the burner face, and means for holding the first burner electrode means at a potential with respect to the electrostatically charged fuel such that the fuel is biased towards the first burner electrode means.
A second burner electrode means may be associated with the burner face, means being provided to selectively electrostatically charge the second burner electrode means at the same polarity as the charged fuel. The second burner electrode means preferably surrounds the first burner electrode means.
A fuel ignition means is conveniently embedded in the burner face and located between a radially inner outlet from a said swirler passage and the first burner electrode means.
The pre-chamber may be provided with pre-chamber electrode means comprising at least a portion of the pre-chamber, charging means being provided to selectively electrostatically charge the pre-chamber electrode means at the same polarity as the charge on the fuel.
Further aspects of the invention will be apparent from the following description and claims.